For women, adolescence is a critical time for building bone mass. In fact, some researchers believe osteoporosis may be prevented or delayed by maximizing bone mass during adolescence. At Ramam Medical Center in Israel, a study found calcium supplementation during the early teen years could provide an extended window for bone mass development.
In this study, 100 girls (about aged 14) with low calcium intakes supplemented with either a placebo or 1,000 mg calcium daily for 12 months. Bone turnover, bone mineral density and bone mineral content of the total body, lumbar spine and femoral neck were measured throughout the study. They found the treatment group had greater development of total-body bone mass density than the control group, and that calcium supplementation was beneficial, especially for girls who were two years into menstruating. They also found that calcium significantly decreased bone turnover.
This benefit from calcium was also noted for older girls during a study from the MRC Human Nutrition Research labs in the UK. In a 15-month study with 144 girls aged 16 to 18 years, the researchers observed whether increases in calcium intake and physical activity could affect the bone mineral status. The participants supplemented with 1,000 mg calcium and were randomly assigned to an exercise or non-exercise group. The researchers found that calcium significantly increased bone mineral content, and that this benefit was more pronounced for the girls who regularly exercised.
Sources: Am J Clin Nutr. 2003 Nov;78(5):993-8; Am J Clin Nutr. 2003 Apr;77(4):985-92